The eye of Petrolisthes elongatus is of the reflecting superposition type. The facets are square and the dioptric apparatus consists of a crystalline cone and a conestalk, each made up of four identical radially arranged units. The rhabdom has an elonagated (2-3 microns diameter) distal segment and a much thicker (6-16 microns diameter) proximal section. The distribution of screening pigments alters dramatically in a migration associated with changes in adaptational state. The following trends with increasing age, monitored as carapace length, were found: (1) increasing number of facets; (2) increasing size of eye and eye-stalk; (3) increasing length of eye-stalk in proportion to eye length; (4) increasing breadth of eye-stalk in proportion to eye breadth; (5) increasing breadth of eye-stalk and eye in proportion to length of eye-stalk and eye; (6) increase in volume of both retinal and dioptric structures; (7) slight increase in rhabdom width; (8) increase in crystalline cone length and breadth and (9) increase in focal length. The results of these trends were presumed to be, firstly, an increase in absolute sensitivity of single ommatidia; secondly, an increase in sensitivity to point sources of light and, thirdly, an increase in angular visual field of the whole eye.
Eremophilus mutisii uses the vascularized central portion of its stomach for aerial respiration, and is a frequent but not obligatory air breather. Air ventilation takes place during a rapid dash to the surface with the expiration of old air preceding inspiration. The frequency of air breathing is affected by aquatic O2 concentration. E. mutisii can survive at least 10 days without air breathing in normoxic water but cannot survive without air access in water containing less than 2.0 ppm O2.
The electroretinogram (ERG) waveform of Petrolisthes elongatus is biphasic and transient and does not change with age (monitored as carapace length and weight of the individual). Though there was a very slight decrease in sensitivity with age (R2 = 0.008), spectral peaks and curves remained virtually unchanged. A shift of 2.2 log units in threshold sensitivity, however, was observed in relation to the different adaptational states. The greatest difference, not unexpectedly, occurred between dark-adapted eyes, tested at night, and light-adapted eyes tested during the day at a background illumination of 250 1x. The gradient of the V/LogI curve (n) in light-adapted animals increased, which means a smaller increase in intensity is required to produce an increase in response compared to a dark-adapted animal, but there was no difference in n with regard to the different age-groups. Also, no significant difference was noticed between dark-adapted eyes tested during day and night. It is concluded that the intensity range over which vision in P. elongatus is maximally sensitive to contrast (the dynamic range) is 2.5-3.0 log units. Since there is apparently little or no alteration in the photic environment and the behaviour of P. elongatus as it ages, there is no advantage in fundamentally altering the parameters of the absolute and spectral sensitivity function with age. Our observations suggest that the eyes are able to adjust within 30 min to changing ambient light levels irrespective of whether or not a circadian activity rhythm operates.
Regenerating retinotectal fibres were visualized by radioautography in turbots (Scophthalmus maximus L.) maintained at 10 degrees-14 degrees C either after crushing one optic nerve or after crushing one nerve and removing the contralateral eye. Regeneration was found to be more extensive 2 days after crushing the right optic nerve than after crushing the left and was further enhanced by contralateral enucleation. The difference between experimental groups was markedly less pronounced by 113 days postoperatively and by 293 days the specimens resembled normal material. Between 113 and 222 days, a transient projection to the ipsilateral tectum was found, which disappeared by 293 days whether or not the contralateral eye had been removed. The differences between the present results and previous findings in symmetrical Cyprinid fish are discussed.
Renal clearance methods were used to observe responses to the posterior pituitary peptide, mesotocin, by the kidneys of adult Ambystoma tigrinum and Notophthalmus viridescens. Ambystoma tigrinum responded to hypophysectomy with a decrease in urine flow and glomerular filtration rate (GFR); however tubular water reabsorption was not affected. Treatment with 5 ng/g mesotocin returned both urine flow and GFR to control levels. Notophthalmus viridescens responded to mesotocin treatment with an increased GFR. Ambystoma tigrinum decreased both plasma [Na+] and [K+] following hypophysectomy, however mesotocin did not reverse these decreases. Urine [Na+] did not change as a result of hypophysectomy alone. This ion increased in urinary concentration following mesotocin treatment of hypophysectomized salamanders. Renal tubular reabsorption of K+ decreased following hypophysectomy; however mesotocin replacement did not reverse this. We consider it unlikely that mesotocin is involved in these tubular responses because of the failure of hypophysectomy and mesotocin replacement to consistently mirror each other.
Oxygen consumption rates (VO2) were measured for painted turtles (Chrysemys picta) swimming in a respirometer at controlled speeds. Sustained specific swimming speeds ranged from 0.75 to 1.52 body lengths (L) per s. Over most of this range endurance exceeded 30 min. VO2 increased curvillinearly with swimming speed (U) and the maximum active rate was 9 times resting (0.26 ml O2/min), and 3 times routine (0.64 ml O2/min). Mass specific metabolic scope was 228 ml O2/(kg.h), similar to that reported for other active chelonians. Cost of transport increased from 3.86 to 5.72 J/(kg.m) over the speed range tested. Swimming costs for rowing painted turtles are greater than those for marine reptiles utilizing anguilliform or lift-producing hydrofoil propulsion. The increased swimming cost for the amphibious painted turtle suggests that morphological specializations permitting effective terrestrial transport, increase energetic expenditures during swimming.
The pineal organ and retina were compared in developing charr and cisco, further in adult cisco, eel, creek chub, dace, zebrafish and black moli by opsin immunocytochemistry. In prehatching charr embryos, retinal rods and cones and pinealocytes displayed well-developed outer segments and formed synapses. Differentiation of the retina started centrally but was more advanced in the dorso-caudal retina than rostroventrally. The pineal organ differentiated earlier distally than proximally. In the cisco, the pineal organ and retina differentiated around hatching. In charr embryos, further in the larval and adult species studied, opsin immunoreactivity was found in retinal rods, accessory cones and many "rod-like" pinealocytes, a result indicating the presence of rhodopsin and/or porphyropsin. Retinal principle cones, long and short cones and some "cone-like" pinealocytes were opsin-immunonegative; they are thought to represent red- and/or u.v./violet-sensitive elements. The pineal organ may be involved in negative phototaxic behavior. Both the retina and pineal organ appear to be suitably differentiated to detect light in the larval and embryonic charr.
The postnatal development of immunoreactivity for photoreceptor-specific markers was studied in mice carrying the genes rd (retinal degeneration) and rds (retinal degeneration slow) in different combinations. Antibodies raised against three specific photoreceptor proteins (opsin, alpha-transducin and S-antigen) were applied on retinae from mice with the following allelic combinations at the rd and rds loci: +/+, +/+ (control); rd/rd, +/+; rds/rds, +/+; rds/+, +/+; and rd/rd, rds/rds. Immunoreactivity for each antibody appeared simultaneously in normal and mutants. Thereafter, the immunoreactivity patterns in the mutants diverged from the normal phenotype. Except for a dramatic loss of photoreceptor cells in the mutants, the main divergence from the normal development consisted of a progressive loss of the intracellular immunoreactivity compartmentalization for each protein. As degeneration progressed, the remaining photoreceptors became homogeneously labelled; one this labelling pattern was acquired, it was maintained during subsequent stages of development. It is proposed that this pattern, common for all phenotypes studied, may be due to the loss of structural and biochemical polarity of the photoreceptor cells undergoing degeneration, and that this may be an important primary or secondary aspect of the disease process.
The CO2 transport properties of the blood of the hagfish, Myxine glutinosa are markedly different from those previously demonstrated for the lamprey, Petromyzon marinus. As in most other vertebrates, the majority of the CO2 in Myxine blood is transported in the form of plasma bicarbonate. Erythrocyte bicarbonate does have some access to the plasma in the blood of Myxine although the documented bicarbonate movements were not sensitive to the chloride/bicarbonate exchange inhibitor, 4,4-diisothiocyanatostilbene-2,2-disulphonic acid (DIDS). The transmembrane pH gradient in hagfish erythrocytes is also quite different from the gradient previously demonstrated in other agnathans. As in other agnathans, significant differences do occur between the distribution ratios for protons, chloride and bicarbonate ions across the erythrocyte membrane, although the magnitude of these differences is smaller in Myxine. Finally, the absence of pH-dependent changes in erythrocyte water content appears to be a common feature of agnathan erythrocytes.
The aim of the present investigation is to study the nature of the ouabain-resistant tracer fluxes of K in rabbit erythrocytes. The data show that the rabbit red cell membrane has a high-capacity, chloride-dependent K transport which is stimulated by osmotic swelling, and which is relatively insensitive to inhibition by loop diuretics, compared to the Na-dependent K transport systems of human and avian red cells. It resembles a system first described in the "LK" (low potassium) sheep erythrocyte, and it is probably the pathway behind the net K efflux which accompanies the regulatory K loss seen in rabbit erythrocytes following osmotic swelling, first recognised by Davson (1937). Further, the rabbit red cell does not show NaKCl cotransport or paradoxical temperature dependence of the "passive leak".
The oxygen consumption rates (VO2) of 9 albacore tuna, Thunnus alalunga (8.5-12 kg) were measured at sea in a swimming respirometer to determine the effects of relative swimming velocity, ambient O2 tension, and water temperature. Significant positive relationships were obtained between tail-beat frequency and relative speed and between relative speed and VO2. The albacore metabolic rate was not appreciably affected by exposure to water temperatures ranging from 13.5 degrees to 16.9 degrees C. Brief exposure to hyperoxia (200-400 mmHg), which was done to reduce the initial stress upon fish in the respirometer, did not affect VO2. Hypoxia (50-99 mmHg), however, did tend to reduce VO2 and affect swimming velocity.
Respiratory and circulatory (measured and calculated) variables were obtained at the same time in resting eels, during normoxia and after 1 h exposure to environmental hypoxia (water PO2 of 40 torr). In normoxia, values of respiratory and circulatory variables appeared less than those reported for most other fish. These differences could be partly explained by a lower level of standard metabolism and a greater uptake of O2 through the skin. Hypoxia caused a marked decrease in heart rate (40%), cardiac output (37%), ventral and dorsal arterial blood pressures (22% and 32%), associated with a constriction of prebranchial veno-venous shunt, and an increase in branchial vascular resistance (30%). Atropine treatment during hypoxia reduced, but did not abolish, bradycardia, and branchial vascular resistance remained unchanged. The lack of increase in cardiac stroke volume as well as the slowing of the heart in atropine-treated eel, could be regarded as metabolic effects of sustained hypoxia. The increase in branchial resistance and constriction of prebranchial veno-venous shunt could be regarded as a direct myogenic effect of hypoxia. Hypoxic exposure resulted in an increase in ventilatory water flow Vg (more than twofold), a decrease in gill O2 uptake (50%) and oxygen partial pressure in arterial (PaO2 80%) and mixed venous blood (PvO2 78%), and in increase in the transfer factor for O2 of the gills, TO2, (+66%). The ventilatory convection requirement increased (fivefold) while extraction (EwO2%) and effectiveness (Eff%) of gill oxygen transfer were maintained in spite of hyperventilation. Hypoxic hyperventilation reduced partial pressure of CO2 (PaCO2 from 3.4 to 0.7 torr) and markedly raised pH (pHa from 7.98 to 8.33) in arterial blood, thus causing a typical respiratory alkalosis, which resulted in increased O2 affinity and capacity of eel haemoglobin.
Commercial interference filters used in much of comparative vision science are constructed to suppress the transmission of light outside the primary passband. However, despite attempts to suppress sideband transmission, it does occur. This sideband transmission can lead to serious problems when working in the ultraviolet (UV) spectrum. The use of UV interference filters with a tungsten source which is calibrated with a silicon photodiode, produce large reproducible errors.
A survey of the eye structure in 10 species of Sagitta (phylum Chaetognatha) which differ in habitat was carried out: 5 epipelagic, 4 mesopelagic and 1 bathypelagic species. Paying attention to the dimension of the pigment cell, and assuming that the perforated lamellae are the photoreceptive regions (PRs), we classified the eyes of the 10 species into 5 types. In type I and II eyes there is one large pigment cell. The maximum length of the pigment cell relative to that of the eye (PC/E) is more than 30% in dorsal view and more than 50% in transverse sections. The pigment cell is surrounded by a wide area of the PR that we designated "central PR". The type II eye possesses, in addition, near the periphery of the eye, masses of PRs which measure about 15% of the central one in size. We call these positionally separated PRs "peripheral PR". In type III eyes the pigment cell and the central PR are small (PC/E is about 10% in dorsal view and less than 40% in transverse sections) and the peripheral PRs are scattered. In type IV eye the pigment cell is also small and the central PRs extend to the periphery. In type V eye the pigment cell is absent and the PR occupies a wide area of the dorsal half of the eye. The type I and II eyes were found mostly in epipelagic species, the type III and IV, in mesopelagic species, and the type V, in bathypelagic species. The adaptational significance of the small pigment cells, the peripheral PRs, and the pigmentless eye is discussed. In addition, we report a new type of photoreceptive cell in mesopelagic Sagitta zetesios, in which two receptoral processes emerge from single cells, in contrast to one in all the other species of Sagitta.
Retinoids in the compound eyes of nymphs and adult dragonflies in 11 families of the 3 suborders were extracted by the oxime method, and analysed by high performance liquid chromatography. Almost all of the species examined contained both retinal and 3-hydroxyretinal in the compound eye. The ratio of 11-cis 3-hydroxyretinal to 11-cis retinal (3-OH ratio) was calculated as an index of the retinoid composition. The 3-OH ratios of the whole eye of nymphs in all the suborders and of adults of the suborder Zygoptera were very high, 2.2 at the minimum, but in Anisozygoptera and Anisoptera most of the ratios were distributed between 1 and 2.7. In the family Gomphidae, exceptionally low 3-OH ratios, less than 1, were observed in several species. The regional distributions of the retinals in the adult compound eyes were also examined. In the Zygopteran compound eye, both retinals were distributed evenly all over the eye, while in the compound eye of the other two suborders, the 3-OH ratios in the dorsal area of the eye were extremely low. In several species of Gomphidae and Libellulidae the ratios in the dorsal areas were zero. From the correspondence of these results and the compartment of the compound eye, it appeared that the large ommatidia in the dorsal area contained only retinal. This was confirmed when the large facet region in the dorsal part of the compound eye of an Anax was excised and examined, and only retinal was detected. However, the ventral area of the true dragonflies' compound eye which did not include the large ommatidia contained both retinals, and the 3-OH ratio was more than ten. The biological significance of using both retinals as chromophores of visual pigments in the dragonfly eye is discussed in relation to the structure of the ommatidia and to the vision of dragonflies.
Gastric evacuation of the juvenile lemon shark, Negaprion brevirostris, a tropical inshore apex predator, was studied in the laboratory under conditions of 25 degrees C and 32% salinity. Sharks were starved for 48-96 h after which they were fed a 2.7% body weight meal of fish fillet. Gastric evacuation was assessed by stomach lavage every 3 h for 24 h thereafter. Results showed that the gut is emptied in about 24 h with fillets being removed from the stomach following the equation Y = Yoe-bt, where Y is percent of meal recovered at time t, Yo is the initial meal size, and b is the instantaneous rate of evacuation. The exponential function of gastric evacuation in the lemon shark is similar to that in teleosts, but the kinetics are slower. The caloric density of the meal remaining in the stomach increased, approaching that of protein in the first 12 h after feeding, as carbohydrates (glycogen) were digested. After 12 h the caloric value dropped as protein was digested, suggesting an orderly and efficient intake of food energy by the lemon shark.
The lactacidosis and hypoxaemia associated with enforced diving in Xenopus leads to a marked increase in circulating catecholamines, a phenomenon not observed during periods of voluntary diving. The magnitude of the catecholamine surge (predominantly noradrenaline) during an enforced dive appears to be matched to the severity of the hypoxaemia and/or acid-base disturbance. Indeed, a strong linear correlation was found between the decrease in arterial pH and the rise in plasma catecholamines that resulted from an enforced 60 min dive. During that time, the levels of plasma adrenaline and noradrenaline showed a strong inverse exponential correlation with arterial oxygen tensions (PaO2). Simultaneous measurements of red cell pH showed that Xenopus does not regulate its erythrocyte pH in the face of a plasma acidosis, unlike the adrenergically mediated pH regulation of red cells of certain teleost fish.
Heart rate, metabolic rate, and tailbeat frequency were simultaneously recorded from seven leopard sharks (Triakis semifasciata) during steady swimming at controlled speeds to evaluate the usefulness of heart rate as a measure of field metabolic rate. Heart rate was monitored by acoustic telemetry using a frequency modulated ECG transmitter. Metabolic rate was measured as oxygen consumption in a swimming tunnel respirometer. For instrumented sharks, mean resting oxygen consumption rate and heart rate were 105.3 +/- 35.6 (SE) mg O2.kg-1.h-1 and 36.6 +/- 1.8 (SE) beats.min-1, respectively. While swimming at the maximum sustained speed (0.84 +/- 0.03 lengths.s-1) for 30-60 min, these rates were 229.3 +/- 13.2 mg O2.kg-1.h-1 and 46.9 +/- 0.9 beats.min-1. Although a significant linear regression was obtained between metabolic rate and heart rate, a low overall correlation coefficient may result from the existence of separate individual regressions and confounding changes in stroke volume and/or arteriovenous oxygen difference. Heart rate was approximately as closely correlated with oxygen consumption rate as swimming speed was. A significant linear relationship was obtained between tailbeat frequency and swimming speed to speeds of 0.75 lengths.s-1.
The fiber glass material Alsynite (Sequentia Corporation) is known to be an effective visual attractant to stable flies, Stomoxys calcitrans. The basis for this attractiveness is not certain, but is found to correlate with high near-UV reflectivity. While examining the transmission properties of Alsynite, it was found that the ratio of short- to long-wavelength photons shifts from 0.17 to 0.77, depending on the angle of the Alsynite relative to the source and the detector. This shift occurs suddenly at an angle of 15 degrees from the normal. To the human eye this shift results in an iridescent blue halo appearing around a light source and at the boundaries of illuminated objects. The phototactic response of stable flies to the 15 degrees off-axis spectral condition, as measured behaviourally, is greater than or equal to their phototactic response to a tungsten source more than 20 times the spectrally corrected intensity. This demonstrates a real preference for the off-axis photon ratio and may in part explain why Alsynite is attractive to stable flies in field situations.
